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David Gruber and his colleagues were on a nighttime dive searching for biofluorescent sea creatures in the coral reefs near the Solomon Islands when when a hawksbill sea turtle glided in front of their cameras. To Gruber’s amazement, the turtle was glowing green and red – the first biofluorescent reptile ever encountered in the wild.

"It was such a short encounter," Gruber tells Laura Geggel for Live Science. "It bumped into us and I stayed with it for a few minutes. It was really calm and letting me film it. Then it kind of dove down a wall, and I just let it go."

While bioluminescent animals like fireflies produce their own light through chemical reactions, biofluorescent creatures actually absorb light and radiate it back out, usually in shades of red or green. While every biofluorescent species has its own reasons for glowing, whether it’s to help them hunt or to hide, scientists have discovered all kinds of marine life that has the ability, from coral and crabs to at least 200 species of fish and sharks, Jareen Imam writes for CNN. While marine biologists have observed loggerhead turtles in aquariums showing signs of biofluorescence, this is the first time the phenomenon has been documented in a wild sea turtle.

"I've been [studying turtles] for a long time and I don't think anyone's ever seen this," Eastern Pacific Hawksbill Initiative director Alexander Gaos, who was not involved in the find, tells Jane J. Lee for National Geographic. "This is really quite amazing."

To cap it off, the fact that the sea turtle gave off both red and green light was remarkable. So far, only one species of coral has been shown to glow green and red and several other hawksbill sea turtles Gruber examined only showed signs of glowing green, Geggel reports. But while Gruber suspects that the red could have come from algae growing on the sea turtle’s shell, he says the green glow definitely came from the turtle itself.

"It could be a way for them to communicate, for them to see each other better, [or] to blend into the reefs," Gruber tells Geggel. "It adds visual texture into the world that's primarily blue."

While Gruber's discovery is the first official realization that the turtles can glow, he suspects that other researchers and photographers have observed the phenomenon in the past without realizing what they were seeing. The blue light necessary to trigger the glow isn't strong enough in shallower waters where the hawksbills are more often seen, Hilary Hanson writes for The Huffington Post.

Right now, more research needs to be done in order to find out why and how the sea turtles glow. However, the species is critically endangered due to climate change, which makes them harder to study as their populations have dropped almost 90 percent in the last few decades, Lee reports. In the meantime, Gruber hopes to study the loggerhead turtles, which are closely related to the glowing hawksbills.

"This is just another example showing how many mysteries the ocean has in store for us,” Gruber tells Imam.

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About Danny Lewis

Danny Lewis is a multimedia journalist working in print, radio, and illustration. He focuses on stories with a health/science bent and has reported some of his favorite pieces from the prow of a canoe. Danny is based in Brooklyn, NY.